FIG. 4 is a plan view showing a general structure of a conventional head element support apparatus, FIG. 5 is a side view of the conventional head element support apparatus, and FIG. 6 shows the principle of support of the conventional head element support apparatus.
The head element support apparatus 1 shown in FIGS. 4 and 5 has a head element 2, gimbals 3 having the head element 2 fixed thereto, and a load beam 4 that supports the gimbals 3 at its tip. The head element 2 has a slider 5 formed of a ceramic material. A magnetic recording unit and a magnetic reproducing unit are mounted on a trailing end surface 5a of the slider 5. The gimbals 3 are formed of an extremely thin leaf spring material. A back surface of the slider 5 is fixedly adhered to the gimbals 3.
The load beam 4 is formed of an elastic plate having a sufficiently larger thickness and a higher rigidity than the gimbals 3. A base of the load beam 4 is a mounting portion 6 to which is fixed to a support 6a that is substantially a rigid body. A portion ahead of the mounting portion 6 is an elastically deformable portion 8. A portion ahead of the elastically deformable portion is a rigid portion 7 that is substantially a rigid body formed by bending both side edges of an elastic plate. As shown in FIG. 4, a central hole 8a is formed in the elastically deformable portion 8 to reduce bending rigidity. A tip of the load beam 4 is integrally formed with a pivot 9 serving as a supporting point. A substantially central portion of a back surface of the slider 5 fixed to the gimbals 3 is supported by the pivot 9.
In the head element support apparatus 1, the head element 2 provided at its tip faces a recording surface of a magnetic recording medium, such as a hard disk. As shown in the principle view of support of FIG. 6, in the head element support apparatus 1, a load pressure F is set depending on a bending elastic force of the elastically deformable portion 8. The load pressure F presses the slider 5 of the head element 2 against the recording medium. Also, the head element 2 is adapted to be swingable about an abutting point between the head element and the pivot 9, as a supporting point, in a rolling direction that is a direction of rotation about a longitudinal centerline Ox and in a pitching direction that is a direction of rotation about a transverse centerline Oy, both directions are shown Ox shown in FIG. 4.
When a magnetic recording medium rotates, airflow above a surface thereof causes a floating force to act on the slider 5. In this case, a floating distance of the slider 5 from the magnetic recording medium is set depending on the load pressure F. Also, as the head element 2 swings in the rolling direction and the pitching direction, the slider 5 can follow up a vertical fluctuation or an inclination fluctuation of the surface of a magnetic recording medium.
JP-UM-A-48-103017 discloses an apparatus in which an auxiliary spring is joined to an intermediate portion of a supporting spring that is a load beam and the supporting spring is pressed by a leading end of an adjusting screw screwed on the auxiliary spring. In this apparatus, it is intended to adjust a pressing force to the supporting spring by the adjusting spring so as to adjust the load pressure acting on the slider.
As described in JP-A-59-112469, an additional auxiliary pressing member is provided on a load beam having a slider at its tip, and the pressing member is formed of a so-called shape-memory alloy that changes in its deformation state depending on temperature. When the apparatus is operated, a rise in temperature within the apparatus causes the shape-memory alloy to exhibit its restoring force, and the restoring force increases a load pressure. On the other hand, when the apparatus is stopped, a fall in temperature reduces a load caused by the shape-memory alloy.
In the current hard disk devices, the recording density of data to the magnetic recording medium becomes extremely high, and accordingly, the dimension of the slider 5 is minimized. Moreover, the floating distance of the magnetic reproducing unit and the magnetic recording unit from the surface of the magnetic recording medium mounted on the slider 5 is also minimized.
As shown in FIG. 6, in the conventional head element support apparatus 1, the load pressure F to be applied to the slider 5 is substantially set by only the bending rigidity of the elastically deformable portion 8 of the load beam 4. However, with a structure in which the load pressure is set by only the bending rigidity of the elastically deformable portion 8 provided at the base of the load beam 4, it is difficult to maintain the balance between the floating force acting on the minute head element and the load pressure, and thus it is difficult to control a floating distance of the slider 5 with little variation.
Further, in the conventional head element support apparatus 1, the posture of the slider 5 is controlled by only the deformation of the gimbals 3 with the pivot 9 as a fulcrum. Therefore, there is a limit to making the slider 5 flexibly follow the recording surface of the magnetic recording medium. In particular, it is difficult to flexibly deform the slider 5 by a minute amount in the pitching direction. Since the slider 5 poorly follows up the recording surface in the pitching direction against fluctuations in height and inclination of the recording surface of the magnetic recording medium, it becomes difficult to control the floating distance of the magnetic recording unit and the magnetic reproducing unit with a high degree of accuracy.
In the head element support apparatus described in JP-UM-A-48-103017, although the adjusting screw that varies spring pressure is provided on the load beam, setting the load pressure using the elastically deformable portion of the one load beam remains unchanged. Similarly, even in the head element support apparatuses described in JP-A-63-29887 and JP-A-59-112469, setting the load pressure using the elastically deformable portion of the one load beam remains unchanged. As such, in the configurations in which the load pressure is set using only the elastically deformable portion of the one load beam, it is difficult to control the load pressure with respect to the slider, as mentioned earlier, and to flexibly set changes in posture in the slider.